View source for 1014 3 User Guide

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<metadesc>The Phidget InterfaceKit 0/0/4 connects to your computer via USB or VINT and has 4 SPDT mechanical relays rated at 210W for DC or 1750VA for AC. </metadesc>

[[Category:UserGuide]]
==Getting Started==
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*1014 Phidget InterfaceKit [{{SERVER}}/products.php?product_id=1014 1014 Phidget InterfaceKit]
*USB cable and computer
*something to use with the 1014 (e.g. power supply and load)


Next, you will need to connect the pieces:
[[Image:1014_3_Connecting_The_Hardware.jpg|600px|link=]]
# Connect the load and power supply in series.
# Connect one end to the 0C (Common) terminal, and the other to the NO (Normally open) terminal.
# Connect the 1014 to your computer using the USB cable.
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==Using the 1014==

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==Technical Details==

===Relays===
A relay is an electrically-controlled switch. Although many types of electrical switches exist, a relay’s mechanical nature gives it the advantage of reliability and current-switching capacity. The main disadvantage to using mechanical relays is their limited life-span, as opposed to solid state relays who do not suffer from this drawback. For more information, check the [[Mechanical Relay Guide]] and the [[Solid State Relay Guide]].

===Using a Digital Output Relay===
[[File:1014_2_Relay_Diagram.jpg|right|300px|link=]]

Relays have a connection scheme determined by the arrangement of contacts within the relay. Because relays are a type of switch, they are defined in the same way other electromechanical switches are defined.

In switch schemes, the number of poles represents the number of common terminals a switch has, and the number of throws represents the number of switchable terminals that exist for each pole. The relays used in the InterfaceKit 0/0/4 are SPDT relays: single pole, double throw. The internal construction of this type of relay is depicted in the diagram above.  Many other types of relays exist:  SPST, DPDT, and DPST, to name a few.

In an SPDT relay, one of the throw terminals is labelled ''normally closed'' (NC), and the other is labelled ''normally open'' (NO).  As the name indicates, the normally closed terminal is the terminal connected to common when the relay coil is not powered. When the relay coil is energized by the relay control circuit, the electromagnetic field of the coil forces the switch element inside the relay to break its contact with the normally closed terminal and make contact with the normally open terminal. The switch element would then connect the normally open terminal and the common terminal.
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===Using Relays as an H-Bridge for Motor Forward/Reverse===
[[File:1014_1_Bridge_Diagram.jpg|right|450px|link=]]

Connect the load (typically a DC Motor) to the COM terminals of the relay. The ''normally open'' (NO) terminals are connected to the power supply (VCC), and the ''normally closed'' (NC) terminals are connected to the ground (GND) of the power supply. You can toggle the corresponding output to switch the relays. 

Looking at the diagram, when LeftCtrl is enabled and RightCtrl is disabled, the current will flow from the NO terminal of relay K1 through the motor and into the NC terminal of relay K2. This will cause the motor to rotate in one direction. 

Similarily, if LeftCtrl is disabled and RightCtrl is enabled, the current will flow from the NO terminal of relay K2 through the motor and into the NC terminal of relay K1. This will cause the motor to rotate in the opposite direction. 

When both LeftCtrl and RightCtrl are disabled, both ends of the motor will be shorted to ground and no current will flow. When both leftCtrl and RightCtrl are enabled, both ends of the motor will be shorted to VCC and again, no current will flow.

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===Wetting Current===
When a relay is in one switch position for a period of time, oxidation of the open contact(s) can occur.  Depending upon the internal coating material of the contacts, oxide films of varying density will be displaced upon the surface of open contacts; this film acts as an insulator to current flow. When the relay is switched, a certain amount of current flowing through the contacts, known as the wetting current, is required to remove the film of oxides and ensure proper conduction. Because of this requirement, these relays are not reliable for signal switching. Check the specification table for your relay board to find out the Minimum Load Current or ''Wetting Current''.

===Load Noise===
If highly inductive loads are used with the InterfaceKit, it is recommended that a noise limiting component be used to prevent damage to the device.  An MOV, TVS diode, or kickback diode (for DC applications) shunted across the load will assist in dissipating voltage transients.

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